测试三种常用的字符串判空串方法所耗的时间，出什么问题了？

[liucom]

using System;
using System.Threading;
public class strLengthTime
{
public static void Main()
{
string strTest="";
string strSub;
for(int i =0 ;i< 1000;i++)
{
strSub=i.ToString();
strTest = strTest + strSub;
}
//System.Console.WriteLine(strTest);
DateTime startTime;
DateTime endTime;
TimeSpan timeCost;
startTime =DateTime.Now;
if(strTest.Length==0)
{
System.Console.WriteLine("Not A Null String!");
}
else
{
endTime=DateTime.Now;
timeCost=endTime - startTime;
System.Console.WriteLine("strTest.Length Method Costs:"+timeCost.ToString());
}
Thread.Sleep(1000);
startTime = DateTime.Now;
if(strTest==String.Empty)
{
System.Console.WriteLine("Not A Null String!");
}
else
{
endTime=DateTime.Now;
timeCost= endTime - startTime;
System.Console.WriteLine("String.Empty Method Costs:"+timeCost.ToString());
}
Thread.Sleep(1000);
startTime = DateTime.Now;
if(strTest=="")
{
System.Console.WriteLine("Not A Null String!");
}
else
{
endTime=DateTime.Now;
timeCost= endTime - startTime;
System.Console.WriteLine("The Third Method Costs:"+timeCost.ToString());
}
}
}

输出的结果都是00：00：00，出什么问题了？

[liucom]

在线等，请各位指教程序到底哪里出问题了

[xiaotupansy]

那里都没有问题，只是电脑所用的时间太短，所以无法显示
using System;
public class strLengthTime
{
public static void Main()
{
string strTest = "";
string strSub;
for (int i = 0; i < 1000; i++)
{
strSub = i.ToString();
strTest = strTest + strSub;
}
DateTime startTime;
DateTime endTime;
TimeSpan timeCost;
startTime = DateTime.Now;
for (int m = 0; m < 100000000; m++)
{
if (strTest.Length == 0)
{
}
}

endTime = DateTime.Now;
timeCost = endTime - startTime;
System.Console.WriteLine("strTest.Length Method Costs:" + timeCost.TotalMilliseconds.ToString());
startTime = DateTime.Now;
for (int m = 0; m < 100000000; m++)
{
if (strTest == string.Empty)
{
}
}
endTime = DateTime.Now;
timeCost = endTime - startTime;
System.Console.WriteLine("String.Empty Method Costs:" + timeCost.TotalMilliseconds.ToString());
startTime = DateTime.Now;
for (int m = 0; m < 100000000; m++)
{
if (strTest == "")
{
}
}
endTime = DateTime.Now;
timeCost = endTime - startTime;
System.Console.WriteLine("The Third Method Costs:" + timeCost.TotalMilliseconds.ToString());
Console.ReadLine();
}
}

[xiaotupansy]

大致上是length的效率最高，empty和""差不多，""稍微好一点

[liucom]

谢谢xiaotupansy(微雨燕双飞)，测试结果出来了，用 string.Length==0方法的速度最快。

[liucom]

我的结果分别是：484.375 ；5218.75 ；4828.125